The invention relates in general to metallurgical operations and in particular to a new and useful process for the production of molded metallurgical coke from coal briquettes which are mixed from dried fine coals or fine coal mixtures with a low swelling index, particularly highly volatile fine coals, with a binder, and pressed to briquettes, rehardened, oxidized, coked and cooled.
A process for the production of molded metallurgical coke from highly volatile fine coal with a low swelling index is known, where the coal must be ground very finely, at any rate below 1 mm. After rehardening and oxidation, if any, of these briquettes which are produced from such coals with a binder, the coking is effected by direct heating, that is, by conducting hot combustion gases over the briquettes. A gas with a low calorific value is obtained which has only limited applications. A large amount of low-grade lean gas is obtained this way from the highly volatile coals. This also reduces the economy of the process. Direct heating causes a great loss of carbon by gasification or combustion, namely about a 4% loss.
In another known process for the production of molded metallurgical coke from highly volatile coal with a low swelling index, the coking of the "green" briquettes which can be subjected, if necessary, to an oxidizing step after-treatment, is effected discontinuously with indirect heat transfer.
In this process, as in the conventional chamber coking process, no measures to prevent emissions are provided or possible. Particularly during the filling of the coal, as well as during the discharge, cooling or quenching of the coke, emission of dust-containing gases, which contain partly combustible or harmful components, are unavoidable.
Emissions also appear to a greater extent because coke cakes, frequently at the bottom end, that is at the outlet of the oven chambers. The cakes must then be crushed by hand with great effort. Dust is produced, which is carried into the atmosphere. Besides, it is very difficult and expensive during the operation of the plant to seal filling hoppers, uptakes and chamber oven doors to such an extent that no gases with tar components can escape.
The above-mentioned methods are described in detail in the report BF V 31 096 of the Battelle Institute Frankfurt e.V.
Presently known methods have thus either a high heat consumption with long coking times and considerable emissions, or there are great carbon losses and only a low-grade lean gas is obtained which has an unfavorable effect on the economy of the operation, particularly when coal with high portions of volatile components is used.